"Fonts can be malicious" made me think of security vulnerabilities in font engines that can be exploited remotely by untrusted websites through things like webfonts. That doesn't necessarily involve Turing completeness, just some bogus memory handling in a font library written in C for instance.
That was my understanding as well, but the links don't corroborate.
Oh, I completely missed that the links were clickable until I read your comments. I thought it was an image.